A metal block of area $0.10$ ${\mathrm{m}}^2$ is connected to a 0.010 kg mass via a string that passes over an ideal pulley (considered massless and frictionless), as in the figure below. A liquid film with a thickness of 0.30 mm is placed between the block and the table. When released the block moves to the right with a constant speed of 0.085 m/s. The coefficient of viscosity of the liquid is:

          
1. \(4.45 \times 10^{-2} ~\text{Pa-s}\)
2. \(4.45 \times 10^{-3} ~\text{Pa-s}\)
3. \(3.45 \times 10^{-2} ~\text{Pa-s}\)
4. \(3.45 \times 10^{-3} ~\text{Pa-s}\)

The terminal velocity of a copper ball of radius 2.0 mm falling through a tank of oil at $20 °\mathrm{C}$ is 6.5 $\mathrm{cm}/\mathrm{s}$. The viscosity of the oil at $20 °\mathrm{C}$ is? (Density of oil is $1.5\times {10}^3 \mathrm{kg}/{\mathrm{m}}^3$, the density of copper is $8.9\times {10}^3 {\mathrm{kgm}}^{-3}$) 

1.   $7.9\times {10}^{-1} {\mathrm{kgm}}^{-1}{\mathrm{s}}^{-1}$

2.   $8.9\times {10}^{-1} {\mathrm{kgm}}^{-1}{\mathrm{s}}^{-1}$

3.   $9.9\times {10}^{-1} {\mathrm{kgm}}^{-1}{\mathrm{s}}^{-1}$

4.   $8.8\times {10}^{-1} {\mathrm{kgm}}^{-1}{\mathrm{s}}^{-1}$